The term "Difficult Terrain" in Pathfinder - Query about Karkadann

[HurinSmite]

Is the term difficult terrain something they kept from 3.5?
I was frustrated when I read the environment part of the CRB that difficult terrain isn't defined. It mentions DF when talking about getting lost and that steep stairs are considered DF. but nowhere does it say "double movement cost, can't charge through it).

What I was expecting when I started reading the wilderness part was that it would say which kinds of terrain would be DF.
Is dense rubble considered DF? dense rubble: "It costs 2 squares of movement to enter a square with dense rubble. The DC of Acrobatics checks increases by 5, and the DC of Stealth checks increases by 2."
Is Bog considered DF? Bog: "It costs 2 squares of movement to move into a square with a shallow bog, and the DC of Acrobatics checks in such a square increases by 2."

Why am I asking about difficult terrain so much? Because I was reading up on the magical beast Karkadann (http://paizo.com/pathfinderRPG/prd/bestiary5/karkadann.html#karkadann).
It has the ability "Sure-Footed (Ex) A karkadann takes no penalty to speed or on Acrobatics or Stealth checks when moving through sandy or desert terrain" that I thought was interesting so I went to check what exactly those penalties are in those terrain types. I couldn't find anything in the wilderness part.

Sort of Related. Isn't it relevant to know what is difficult terrain if I pick the feat nimble moves?

[Geddy2112]

It is in the combat section "Difficult Terrain:Difficult terrain, such as heavy undergrowth, broken ground, or steep stairs, hampers movement. Each square of difficult terrain counts as 2 squares of movement. Each diagonal move into a difficult terrain square counts as 3 squares. You can’t run or charge across difficult terrain. If you occupy squares with different kinds of terrain, you can move only as fast as the most difficult terrain you occupy will allow. Flying and incorporeal creatures are not hampered by difficult terrain."

Dense rubble is normally considered difficult terrain, as are bog's. However, not all difficult terrain impacts stealth or acrobatics. Each terrain has their own modifier.

For the desert, it means the Karkdann does not take penalties one would normally take on acrobatics and stealth checks so long as it is in the desert. That said, sand and most terrain's don't imply a mechanical penalty to stealth or acrobatics, but instead increase the DC. This is likely a "penalty" RAI but not RAW. Deserts make stealth difficult because they lack sufficient concealment, but this is not a penalty. Sand increases the DC of acrobatics checks by 2, but this is again not a penalty. I do know a Karkdann can move at full speed in a desert and charge or run in the sand, but it would be up to a DM if they got off on the DC to acrobatics or could move at full speed in the sand without penalty.

[Necroticplague]

Actually, it does say that stuff.

Hampered Movement

Difficult terrain, obstacles, and poor visibility can hamper movement (see Table: Hampered Movement for details). When movement is hampered, each square moved into usually counts as two squares, effectively reducing the distance that a character can cover in a move.

If more than one hampering condition applies, multiply all additional costs that apply. This is a specific exception to the normal rule for doubling.

In some situations, your movement may be so hampered that you don’t have sufficient speed even to move 5 feet (1 square). In such a case, you may use a full-round action to move 5 feet (1 square) in any direction, even diagonally. Even though this looks like a 5-foot step, it’s not, and thus it provokes attacks of opportunity normally. (You can’t take advantage of this rule to move through impassable terrain or to move when all movement is prohibited to you.)

You can’t run or charge through any square that would hamper your movement.
So, at least for the 'double movement cost, can't charge', PF still has those rules on its own accord.

So while Bog and Rubble don't seem like they technically don't count as Difficult Terrain, they definitely fall in the same category of 'hampered movement' as Difficult Terrain does, and carry the same penalty of no charging through.

[BowStreetRunner]

Keep in mind that sandy or desert terrain can include both difficult and normal terrain. So the Karkadann would not be hampered by broken ground in sandy or desert terrain, but would be hampered by broken ground in the tundra or a jungle.